There is known a connector mounted to a circuit board in a press-fit manner. For example, a connector 200 illustrated in FIG. 1 includes a press-fit pin 201 press-fitted into a through-hole 101 formed in a circuit board 100. The press-fit pin 201 is formed such that its distal end portion to be inserted into the through-hole 101 has a width larger than an inner diameter of the through-hole 101 and is elastically deformable. When the distal end portion of the press-fit pin 201 is inserted into the through-hole 101, the distal end portion is pressed against the inner wall surface of the through-hole 101 such that electrical conduction is ensured.
In the press-fit-type connector 200, when the press-fit pin 201 is press-fitted into the through-hole 101, the distal end portion of the press-fit pin 201 may abut against an edge portion of the through-hole 101 and buckle without being properly inserted. This may be caused, for example, when the distal end portion is bent in a manufacturing process of the press-fit pin 201. It is also considered that the press-fit pin 201 buckles due to a worker's inadvertent handling such as, for example, touching the distal end portion or causing the distal end portion to come into contact with something during the press-fitting of the press-fit pin 201. Thus, after the press-fit pin 201 is press-fitted, the rear surface side of a circuit board 100 is visually observed, and the presence or absence of buckling of the press-fit pin 201 is determined based on whether the distal end portion of the press-fit pin 201 protrudes from the rear surface of the circuit board 100.
However, in recent years, the length of such a press-fit pin 201 has been shortened according to high-speed signal transmission. As illustrated in FIG. 2, there is a case in which the distal end portion of the press-fit pin 201 inserted into the through-hole 101 may not protrude from the rear surface of the circuit board 100. In such a case, it becomes difficult to confirm the presence or absence of the press-fit pin 201 by a visual observation.
Furthermore, in recent years, there is also a case in which connectors 200 are provided on the front and rear surfaces of a circuit board 100 and press-fit pins 201 are press-fitted at the opposite sides of the same through-hole 101. In such a case, it was conventionally difficult to confirm, by a visual observation, the presence or absence of buckling of the press-fit pin 201 press-fitted into the same through-hole 101 from the rear side.
In this regard, there is a case in which a conduction failure caused by the buckling of the press-fit pin 201 may be detected by performing a conduction test of the press-fit pin 201 and the circuit board 100 after the press-fit pin 201 is press-fitted. However, even in this case, it is necessary to repeat a press-fitting work of the press-fit pin 201, which may cause the degradation of production efficiency. Moreover, there is a case in which a press-fit pin 201 passes a conduction test even though the press-fit pin 201 is buckling after it is press-fitted. In this case, the press-fit pin 201 and the circuit board 100 may be insulated due to environmental factors such as, for example, temperature fluctuation and vibration generated after shipping of a product, and a conduction failure may be generated in the shipped product.
In connection with this, there has been proposed a connector in which a through-window is provided in a press-fit portion that holds a press-fit pin to check the buckling of the press-fit pin.
When it happens that a buckling press-fit pin exists in the position of the through-window, the buckling of the press-fit pin may be found. However, when the position of the buckling press-fit pin is different from that of the through-window, it is difficult to find the buckling of the press-fit pin. In addition, the work of confirming the presence or absence of buckling in the press-fit pin by looking in the through-window is never easy from the beginning since it takes much time and effort.
The followings are reference documents.                [Document 1] Japanese Laid-Open Patent Publication No. 2012-216293 and        [Document 2] Japanese Laid-Open Patent Publication No. 2002-237664.        